Mud screen filters are used generally to filter drilling fluid before it flows down the inside of a drill string. The purpose is to prevent trash, debris or excessive solids or drill bit cuttings from entering or re-entering the drill string, so as to reduce the chance of plugging or clogging downhole tools to a point where they will not operate properly. The two most common conventional locations for placement of a mud screen are: (1) inside of the box end connection of the top joint of pipe as drilling occurs; and (2) further down the drill-string as an in-line mud screen.
Mud screens are conventionally “dropped into” the drill string at a joint of drill pipe as a new length of pipe is added to the string on the rig floor. See FIGS. 1A through 1D, and video at https.//youtu.be/KZxUiFFrVEAQ (particularly at about 1:05-1:15 minutes). FIGS. 1A through 1D depict the prior art as herein described. FIGS. 1A and 1B are schematic depictions of conventional drop-in mud screen 120 being inserted between pipe joints 110 and 130. FIG. 1A schematically shows mud pumps 150 delivering fluid flow F of drilling fluid to rig 100. FIG. 1B is an enlargement of FIG. 1A. FIG. 1C is an enlargement in section of conventional drop-in mud screen 120 as typically inserted between pipe joints 110 and 130. FIG. 1D is a flow chart describing the typical process of inserting conventional drop-in mud screen 120 between pipe joints 110 and 130. FIG. 1B is an enlargement of FIG. 1A at the rig floor, and FIG. 1C is a section through the drill string with mud screen installed at a pipe joint.
FIG. 1D depicts a flow chart 200 describing the general process illustrated on FIGS. 1A through 1C and as shown on the above-cited prior art video. Generally, the process involves first separating pipe joint 110 from pipe joint 130 per FIGS. 1A through 1C, or as described on flow chart 200, separating a top drive from old joint no. 1 (block 201) in situations where screen 120 is located at the top of a drill string before connection to a top drive. Screen 120 is removed and, if necessary, replaced (block 202). A new pipe joint is appended to the top of the old joint no. 1, becoming new joint no. 1 below the top drive (see block 203 on FIG. 1D), or alternatively becoming a new pipe joint 103 per FIGS. 1A through 1C. Mud screen 120 is dropped into new joint no. 1 (block 204), or alternatively into new pipe joint 130 per FIGS. 1A through 1C). The top drive is then reconnected to new joint no. 1 (block 205 on FIG. 1D), or alternatively pipe joint 110 is reconnected to new pipe joint 130. In either case, screen 120 has moved up one connection between pipe joints towards the rig as an additional pipe joint has been added to the drill string.
FIG. 1E in U.S. Provisional Application Ser. No. 62/560,652, incorporated herein by reference, depicts various types and styles of conventional drop-in mud screens that might be used in the prior art methods described with reference to FIGS. 1A through 1D. Users may select from among a combination of different shaped openings and/or mesh screens for screening out desired solids or other items.
There are at least three disadvantages of conventional drop-in mud screens as used in the prior art as described above. First, the mud screens can cause significant damage to the drill pipe connections, requiring cost and time to repair. As shown on FIG. 1C, some lengths of drill pipe may require special end connections 135 deployed to receive the mud screen. Such special end connections add expense to the cost of drill pipe, and may further require their own additional repairs if damaged.
Second, if a well control situation occurs, the presence of a drop-in mud screen in the drill string may (for example) restrict mud flow, and thus may become a serious impediment to regaining control of the well.
Third, as depicted in the prior art video cited above, removal and re-insertion of a drop-in mud screen adds additional steps, and therefore time, to the process of inserting additional pipe joints in a drill string. Time is always of the essence in drilling operations. Also, additional steps may bring additional personnel safety concerns. Further, operators may forget to remove or re-insert drop-in mud screens during an extended drilling operation. In such cases, redundant additional drop-in screens may be left in the drill string, or drill strings may operate for periods with no screen in place. Either situation is not optimal for efficient solids control.